Pointing devices such as mice have been widely employed in computer systems or other electronic apparatuses equipped with a display screen so as to control movement of a cursor on the display screen or scroll an image relative to the display screen. In addition, the pointing device may be actuated to generate responsive setting signals to conduct further data processing operations. As known, a scroll wheel assembly is usually provided on a pointing device and used by the computer operators to scroll an image relative to the display screen. Since the scroll wheel assembly is rotatable in either a forward direction or a backward direction, the image would be scrolled upwards or downwards. For a purpose of controlling movement of the cursor by the scroll wheel assembly, another type of pointing device with a sensing member on either or both sides of the scroll wheel assembly was developed. An example of the sensing member is a strain gauge. By laterally stirring the scroll wheel assembly, the sensing member is actuated to generate a control signal. In response to the control signal, the cursor shown on the display screen would be located to move in the left or right direction accordingly.
This pointing device, however, has several drawbacks. For example, since the sensing member is typically arranged on bilateral sides or peripheries of the scroll wheel assembly, the overall volume of the pointing device fails to meet the growing requirement of minimization. In addition, the approach of laterally stirring the scroll wheel assembly may lead to excessive swing amplitude, and thus the scroll wheel assembly is hard to be precisely controlled.